The most commonly seen electric motor is mainly composed of a rotor and a stator winded with induction coils. The rotor can have many different types and can be formed of different materials. The most common type of the rotor includes copper rotor, aluminum rotor and squirrel-cage rotor. The squirrel-cage rotor generates an induced current through the conductors and is driven to rotate by the induced magnetic field.
Although the copper rotor has high rotor efficiency, the copper rotor is subject to problems such as difficulty in casting and high mold loss. Although the aluminum rotor is easier to cast, the aluminum rotor has higher resistance and higher loss. As for the squirrel-cage rotor, the soldering quality of conductors is unstable, and the casting process still have problems such as the flow of liquid metal being unsmooth, the distribution of the current being non-uniform, and the dynamic balance of the rotor being difficult to calibrate. Thus, how to provide a rotor having satisfactory efficiency and manufacturability and at the same time meeting the high quality requirement has become a prominent task for the industries.